The present invention relates to a device for measuring and/or monitoring the intraocular pressure (IOP). The present invention relates in particular to a device that can be placed on the eye of a user to monitor intraocular pressure over an extended period of time, for example 8 hours, 12 hours, 24 hours or more.
Glaucoma is a widespread disease characterized by an elevated intraocular pressure (IOP). This elevated IOP produces a gradual loss of peripheral vision. There is therefore a need to have a detailed knowledge of IOP in glaucoma patients in order to provide reliable diagnostics or for setting up new therapies.
U.S. Pat. No. 4,922,913 describes an intraocular pressure sensor having a piezo-resistance strain gauge cell mounted in a curved holder which serves to position the planar pressure sensitive surface of the strain gauge cell against the surface of an eye. This sensor is specifically designed to be placed on the sclerotic portion of the eyeball (sclera), so that the pressure sensitive surface presses on the white part of the eye. The sensor is small, so that, when placed on the sclera, it is off-centered relative to the eye and it doesn't cover the cornea. The curved holder is made similarly to a hard contact lens.
A drawback of this intraocular pressure sensor is that it cannot be worn without interruption over extended periods of time because, like hard contact lenses, such a rigid holder rapidly provokes unbearable discomfort. Furthermore, the sensor is connected with wires to an external recording/monitoring apparatus, which is uncomfortable and requires that the recording/monitoring apparatus is kept relatively close to the user's head.
Another drawback of the pressure sensor of U.S. Pat. No. 4,922,913 is that a hard and small off-centered curved holder will significantly slide and move on the eyeball, thus resulting in uncontrolled changes of the measurements' conditions and thereby compromising the accuracy of the IOP measurement. In order to avoid significant displacements and to maintain it in good contact with the eyeball, the curved holder of U.S. Pat. No. 4,922,913 must be placed under the eyelid.
Yet another drawback of this intraocular pressure sensor is that the rigid holder must be manufactured or at least customized specifically for each user. A hard holder must indeed be perfectly adapted to the particular shape and size of the user's eyeball for it to properly fit and not disturb the user when worn. This individualization of the sensor thus increases its manufacturing costs.